Steven A. Tananbaum Senior Fellow for International Economics Robert Kahn writes that financial markets rallied following the U.S. election, on hopes that President-Elect Donald J. Trump’s fiscal stimulus and deregulation initiatives would spur corporate profits and growth. Perhaps so, but a strong case could be made for the opposite: that Trump’s economic agenda will prove disruptive to trade and growth, face growing headwinds in Congress, and exert a contractionary impact on the U.S. economy.

Military budgets are only one gauge of military power. A given financial commitment may be adequate or inadequate depending on the number and capability of a nation's adversaries, how well a country …